This invention relates to a device for identifying coin type articles, encompassing all of the coin types known to those of ordinary skill in the art on the basis of the diameter thereof, comprising
a coin path for feeding coins;
a light source for illuminating the coin on the path in a direction essentially perpendicular to the plane of the path; and
a photosensitive sensor for converting the light which passes the coin into an electric signal dependent on the diameter of the coin, or the like.
In coin identification devices of the above type, the light receivers are formed, either by optic fibres the ends of which are arranged at suitable heights in accordance with the diameters of the different coin types, or by columns consisting of photodiodes or some other photosensitive elements. These kinds of devices for determining the diameter of a coin, are known e.g. from British Patent Applications 2 115 547 and 2 176 038 and British Patent specifications 1 379 473 and U.S. Pat. No. 4,249,648. The use of a sensor according to British Patent Application 2 176 038 requires that the coin be in contact with the path when it passes the sensor. On the other hand, this kind of sensor arrangement merely enables the different coin types to be separated from each other, whereas foreign coins, for instance, which fall between these coin types are included in the group of the next smallest coin type, and it is not possible to exclude them from the counting. Further, when this kind of device is modified so as to be operative with another country's coins, a new basic adjustment is required, i.e. the fibres have to be arranged at suitable heights through experimentation. The devices disclosed in British Patent Application 2 115 547 and British Patent Specifications 1 379 473 and U.S. Pat. No. 4,249,648 utilize photodiode rows, by means of which the size of a coin or some other object can be determined on the basis of the number of photodiodes shadowed by the coin. The sorting accuracy of devices of the above type could possibly be improved by increasing the number of the fibres or photodiodes, whereby, in theory, it would be possible to determine the diameter very accurately. In practice, however, the formation of a measuring sensor consisting of a great number of fibre ends or photodiodes is difficult and, in any case, causes considerable costs on account of the complicated structure as well as requiring the detector to be attached to each fibre or photodiode.
Swedish Patent Specification 397 420, in turn, discloses apparatus capable of identification of coins, or the like, on the basis of the area thereof. In a device according to this publication the light receiver consists of a large-area sensor formed by four solar cells, by means of which sensor the area of the coin can be determined on the basis of the total amount of light gone passing the measuring point at the measuring moment. For obtaining a correct measuring result, there must not be more than one coin at a time within the measuring area, which, retards considerably the operation of the device. Moreover such a device has to be provided with means for preventing more than one coin entering the measuring area. In addition, the calibration of the responses of the different parts of the large-area sensor in such devices is also difficult, if not impossible.